JP7744981B2 - Method for dispensing powder from an intermediate reservoir in a powder bed fusion bonding apparatus and corresponding device - Patents.com - Google Patents

Description

The present invention relates to additive manufacturing, also commonly known as 3D printing. More specifically, the present invention relates to improvements to a powder bed fusion process, a corresponding powder dispenser, and a powder bed fusion apparatus equipped with the dispenser.

2. Description of the Related Art Additive manufacturing is an increasingly important method capable of producing 3D workpieces. While a variety of different additive manufacturing methods exist, this specification focuses on methods and apparatus for joining powder particles, e.g., by selectively heating particles on a bed of powder particles to bond some particles together. The powder particles are bonded to each other by sintering, fusing, and/or welding. Heat for these processes is typically provided by preferably focused radiation, e.g., an electron beam or laser beam, to selectively heat portions of an upper layer of the powder bed, thereby causing particles in the upper layer to adhere to particles in the preceding layer and to adjacent particles in the upper layer. This process is generally referred to as powder bed fusion bonding or simply powder fusion bonding. This specification does not distinguish between different types of radiation and simply refers to them as "beam."

Modern apparatus for powder bed fusion bonding include a housing with a process chamber. The process chamber has a support opening for receiving a movably supported workpiece support. First, a thin layer of powder is applied to the workpiece support. This is primarily achieved by a recoater. The recoater is a vehicle that is driven back and forth across a bottom opening, thereby coating the workpiece support with a layer of powder. Recoaters are described in many publications, such as WO 2018/156264, WO 2017/143145, EP 1234625, and DE 102006056422, to name just a few. These recoaters can be broadly divided into two groups:
(i) Powder is supplied to the bottom of the process chamber, for example, through an opening next to the support opening, and then distributed by a distributor, which is considered herein a "type (i) recoater," and typically has at least one blade, roller, lip, or similar means configured to move across the support opening, thereby forming a new layer of powder on the workpiece support.
(ii) A powder reservoir is movably supported for movement across the support opening, thereby providing a new layer of powder onto the workpiece support ("type (ii) recoater"). Type (ii) recoaters often also include one or more dispensers for leveling, or grading, the powder layer. Recoater reservoirs are referred to herein as "recoater reservoirs" and "recoater reservoirs."

As a new layer of powder is applied, at least one beam is moved across the upper layer of the coated surface, causing some powder particles to bond to each other and, in some cases, to the workpiece support. The workpiece support is then lowered, and the recoater applies the next layer of powder. This next layer is also exposed to the beam to selectively bond the powder particles to each other and to the structure of the previously bonded particles. The process of lowering the workpiece support, applying a new layer of powder, and "writing" with the laser is repeated, resulting in a 3D object. This process has been described in numerous publications, such as U.S. Patent Application Publication No. 2017/0001243 and U.S. Patent No. 9,061,465, to name just two.

German Patent Application Publication No. 102004022387 discloses a recoater for a powder bed fusion bonding apparatus equipped with a circular blade for distributing powder. The circular blade surrounds a linearly extending grid of blades, and in this sense comprises a linearly extending grid of blades. A new layer of powder is provided by using the circular blade to press the powder across the support openings. As taught in German Patent Application Publication No. 102004022387, the circular blade shears particle agglomerates, which is reported to result in a denser powder layer with reduced roughness. To further improve the density of the powder layer, it has been proposed to couple the circular blade to an ultrasonic generating means.

German Patent No. 10117875 proposes providing a new layer in a powder bed fusion process by using a type (ii) recoater having a blade to provide a thin, homogenous powder layer. The blade is rotatably supported and driven to perform a rotational oscillation. During operation, powder is delivered from a powder storage chamber to a recoater reservoir. From the recoater reservoir, the powder is deposited in front of the rotationally oscillating blade and is pushed onto the existing powder bed using a rotational oscillation drive. This rotational oscillation is believed to break up agglomerates of particles in the powder and homogenize the powder while providing a thin powder layer.

Whether the recoater is a type (i) or type (ii) recoater, powder is dispensed from an intermediate reservoir (also referred to as a storage chamber) into either the bottom of the process chamber (if a type (i) recoater is used) or into the reservoir of the type (ii) recoater. In currently used powder bed fusion systems, dispensing of powder from the intermediate reservoir into the recoater reservoir is accomplished by a rotary feeder (this is considered to include the case of dispensing onto the bottom of the process chamber; the location where powder is dispensed from the storage chamber can be considered to form the recoater reservoir of a type (i) recoater).

The rotary feeder has an elongated "feed wheel," which can be thought of as a feed shaft. The feed shaft spans the width of the support opening. The feed shaft has one or more notches extending along the feed shaft's rotational axis. When the notch faces upward into the downward-facing discharge opening of the intermediate reservoir, powder slides into the volume of the notch. Rotation of the shaft forces the notch downward, thereby emptying the notch; that is, powder pours from the notch into the recoater reservoir. In other words, each rotation of the notch is expected to deliver a predefined amount of powder into the recoater reservoir.

SUMMARY OF THE INVENTION The present invention is based on the observation that notches in the feed shafts of current powder bed fusion apparatuses must be manufactured by costly milling and grinding processes. Furthermore, the feed shafts are difficult to seal, as required to reduce inert gas leakage and powder particle shedding from the process chamber. Furthermore, metering of the dispensed powder volume can only be adjusted to an integer multiple of the notch volume, and is further compromised by powder bridges that form across portions of the discharge outlet of the intermediate reservoir. Based on these observations, the problem underlying the present invention is to improve the loading of the reservoirs of the recoaters of powder bed fusion apparatuses.

The solution to this problem is described in the independent claim. The dependent claims relate to further developments of the invention.

For example, the above-mentioned problem can be solved by a dosing device for a powder fusion bonding apparatus. The dosing device may have a powder inlet, via which the dosing device can receive powder from a discharge opening of a powder storage chamber. In practice, these powder storage chambers are positioned inside the process chamber or at least have a discharge opening. This discharge opening connects the storage volume of the storage chamber to the process chamber via the discharge opening. "Connecting" in this context means enabling the transfer of powder from the storage chamber to the process chamber. The storage chamber is an intermediate powder reservoir of the powder supply system. In this specification, the terms storage chamber or powder storage chamber are used simply to linguistically distinguish between the recoater reservoir and the intermediate reservoir (= storage chamber). In other words, the terms powder storage chamber and storage chamber can be replaced by intermediate powder reservoir without changing the technical teachings of this application and the patents granted thereto.

In summary, the dosing device is configured to receive powder from the storage chamber. For example, the powder inlet of the dosing device may be positioned immediately below the discharge opening of the storage chamber, thereby allowing powder to be supplied to the powder inlet of the dosing device by powder falling from the discharge opening of the storage chamber.

The metering device has a powder outlet configured to drop powder into a recoater reservoir of the powder fusion bonding device. The recoater reservoir may be the reservoir of the type (ii) recoater, or may simply be a location on the base plate (i.e., bottom) of the process chamber from which powder is dispensed by the type (i) recoater.

Between the powder inlet of the metering device and the powder outlet of the metering device is a powder support. The powder support is configured to receive powder through the powder inlet and to transport the powder to the powder outlet. As the word implies, the powder support supports the powder, i.e., the powder support holds the powder in a predetermined position on the powder support until it is transported to the powder outlet by the transport means. In one example, the powder support may be a plate or board positioned below the powder inlet.

Preferably, a gap exists between the powder inlet and the powder support. The gap defines the maximum height of powder that can accumulate on the plate. Therefore, the gap is preferably larger than the particle size determined by the metering device. Preferably, the height of the plate and/or the height of the powder inlet are adjustable, thereby making it possible to adjust the gap height. For example, at least one of the powder support and the powder inlet may be removably attached to a metering device support structure having a predetermined vertical extension length and/or an adjustable vertical extension length, thereby making it possible to adjust the gap.

The powder support may be sloped toward the powder outlet. Preferably, however, the slope is below a critical slope, defined as the slope at which the static friction force and the downhill force have the same absolute value. Therefore, increasing the slope above this critical slope will cause the powder to slide on the powder support. In other words, increasing the slope of the powder support above the critical slope will turn the powder support into a chute.

In another example, the powder support comprises a grate, i.e., a sieve. The term grate is used solely for linguistic distinction with respect to any other sieve described below. Therefore, the term "first sieve" may be used herein instead of "grate." The mesh size of the grate is larger than the powder particles designated to be dispensed by the metering device. Preferably, the mesh size of the grate is at least two times larger than the powder particles, and particularly preferably, the mesh size of the grate is at least three times larger than the powder particles. Furthermore, the mesh size is smaller than the critical mesh size, which is defined as the mesh size at which powder falls through the stationary grate.

In a preferred embodiment, the powder support of the metering device is coupled to an ultrasonic transmitter and/or a vibratory drive (collectively referred to herein as a "drive"). The ultrasonic waves and/or vibrations reduce the critical gradient and angle of repose of the powder on the powder support, respectively. Thus, if the powder support is a board or plate, the powder slides toward the powder outlet. Simply for the avoidance of doubt, "coupled" in this context refers to a mechanical connection that allows the ultrasonic waves generated by the ultrasonic transmitter to propagate to the powder support, e.g., a grid mesh. When the vibratory drive is "coupled," it refers to a mechanical connection between the vibratory drive and the powder support (e.g., a grid mesh), which transmits the vibrations of the vibratory drive to the powder support. The vibrations are considered to be a movement of the grid mesh, which may be "back and forth" or "up and down," or a combination thereof. The vibratory drive can vibrate the powder support, e.g., between two positions and/or orientations, and/or induce at least one normal mode of the powder support. All of these vibrations provide a reduction in the critical tilt angle and/or the critical angle of repose, thus causing a portion of the powder to flow into the recoater reservoir. In the case of ultrasonic excitation, the ultrasonic waves propagating through the powder support also reduce the critical tilt angle and the critical angle of repose. Furthermore, the ultrasonic waves can also propagate through the powder, thereby "fluidizing" the bulk material, as it were, and similarly causing powder flow into the recoater reservoir. As is conventional, the ultrasonic transmitter herein is also referred to as an ultrasonic generator and transmitting ultrasonic transducer.

The energy of the vibration and/or ultrasonic excitation allows for stepwise control of the fluidization, i.e., the volume of powder per unit time delivered to the outlet can be adjusted by increasing or decreasing the excitation. For a given excitation of the powder support, the delivery speed is constant, and therefore the amount of powder to be dispensed into or into the recoater reservoir can be adjusted by selecting the duration of the excitation. In practice, the operation of the drive device is preferably controlled by a control device.

As already mentioned above, the powder support preferably comprises a mesh that is coupled to an ultrasonic transmitter and/or a vibration driver and is configured to allow powder to flow through the mesh by exiting the mesh upon operation of the ultrasonic transmitter and/or vibration driver.

Preferably, the powder support comprises a frame, and the grid is supported by the frame and is preferably mechanically attached to the frame. This measure provides a stable grid and allows the ultrasonic transmitter and vibration drive to be securely coupled to the grid via the frame. Furthermore, the frame simplifies sealing of the powder support to the housing of the metering device.

The connecting elements can connect, i.e., mechanically attach, the lattice network to an ultrasonic transmitter and/or vibration driver via the frame.

For example, the metering device may include a feeder housing with a powder passage. The powder passage is defined by a passage wall of the housing. The powder passage may connect a powder inlet and a powder outlet. Preferably, a lattice network is positioned transversely to the longitudinal extension of the powder passage, thereby dividing the powder passage into an upper passage portion facing the inlet and a lower passage portion facing the outlet. In the case of a straight passage, the longitudinal extension of the powder passage can be considered to be defined by the longitudinal passage axis. In the case of a curved passage, the neutral axis of a curved beam assumed to be installed within the passage can be considered to define the longitudinal extension direction of any infinitesimal passage segment. By transverse, it is meant that the lattice network intersects the powder passage at an angle, preferably, but not necessarily, a right angle (±15°, preferably ±10°, even more preferably ±5° or less). The angle may preferably be between 60° and 120°.

The housing may support a powder support. For example, the passageway wall may form a recess into which the powder support sealingly engages. This allows for easy assembly while simultaneously preventing bypass powder. Similarly, the powder support may include a recess into which a protrusion on the passageway wall sealingly engages.

Particularly preferably, an elastic member is positioned between the powder support and the housing. This prevents direct transmission of vibrations from the powder support to the housing, while sealing the gap between the powder support and the housing. Therefore, other components of the powder bed fusion bonding apparatus are less stressed by ultrasound and/or vibrations, improving their lifespan and operational accuracy. This can improve the quality of the workpiece.

As is clear, the dosing device may be installed in a powder bed fusion bonding apparatus, also referred to as a "powder fusion bonding apparatus." The powder fusion bonding apparatus may include at least a process chamber and a powder storage chamber with a powder drop opening, the discharge opening of which is fluidly connected to the process chamber. A recoater reservoir may be positioned within the process chamber. The powder inlet of the dosing device is preferably positioned below the discharge opening of the powder storage chamber. This ensures that the powder flow from the discharge opening is stopped when the powder inlet of the dosing device is filled with powder. Powder delivered to the recoater reservoir is immediately replenished by gravity. The powder outlet of the dosing device is preferably positioned above the parking position of the recoater. In this case, the powder outlet of the dosing device can directly feed the recoater reservoir when the recoater is parked at its parking position. As is common, the recoater may be positioned on a parking spot, or so-called parking position, between multiple coating cycles. The recoater reservoir can therefore be refilled between these coating cycles via the powder outlet of the dosing device.

Preferably, the powder storage chamber has a powder inlet opening. As is typical, the powder inlet opening may be connected to a powder distribution system for transporting powder to the storage chamber via the powder inlet opening of the storage chamber. Powder may be supplied, for example, via a powder supply line from a main tank and/or an excess powder removal trap in the process chamber. From these powder sources, fresh powder is provided to the storage chamber by a powder transport system. For example, a pneumatic transport system may be used, and the transport gas flow is preferably an inert gas flow. In a particularly preferred example, the powder inlet opening is protected by a sieve (to be distinguished from a first sieve, i.e., a grid) for separating particles exceeding a predetermined size. This (second) sieve therefore has a (second) sieve mesh size and separates particles exceeding the sieve mesh size. Therefore, these particles cannot be transported into the storage chamber along with the powder.

As already clear, the grid mesh has a mesh size that is preferably larger than the sieve mesh size, thereby preventing the accumulation of particles to be removed in the process chamber. This ensures particularly high metering accuracy, primarily because the free area of the grid mesh is not reduced over time by particles clogging the grid mesh. This improves the quality of the workpieces produced. The grid mesh and sieve can be combined to form a single grid mesh. In particular, in this case, the metering device can include a grid mesh residue removal slider. The grid mesh residue removal slider can be configured to scrape residue from the grid mesh into a residue reservoir. For example, the grid mesh residue removal slider can be movably supported by at least one guide rail and/or telescopic arm positioned upstream of and/or near the grid mesh. Preferably, the mesh residue removal slider is connected to a drive for advancing the mesh residue removal slider from a first position on the upstream-facing mesh surface to a second position and for returning the mesh residue removal slider to the first position.

A method for filling a reservoir of a recoater of a powder fusion bonding apparatus with powder may include at least the step of discharging powder from a powder storage chamber onto a metering device, such as a powder support of the metering device as described above. Furthermore, the method may include the step of exciting phonons in the powder support of the metering device and/or vibrating the powder support relative to the process chamber boundary and inducing normal modes of the powder support. Each of these means allows for controlled transport of powder through the outlet of the metering device to the recoater reservoir.

The present invention will now be described by way of example only, without limiting the overall concept of the invention, with reference to the accompanying drawings.

FIG. 1 illustrates a first example of a powder bed fusion bonding apparatus. FIG. 1 illustrates a second example of a powder bed fusion bonding apparatus. 1 is a vertical cross-sectional view showing an example of a metering device. 5 shows the metering device of FIG. 4 in a cross-sectional view perpendicular to the view shown in FIG. 3;

The powder bed fusion apparatus 1 shown in FIG. 1 includes a process chamber 10 defined by a process chamber housing wall 12. During operation, the process chamber 10 is preferably filled with an inert gas. In a preferred embodiment, a flow of inert gas enters the process chamber 10 through at least one first opening in the process chamber housing wall 12 and exits the process chamber 10 through at least one other opening.

The process chamber 10 has a base plate 11, which may be considered the bottom 11 of the process chamber 10. A support opening 14 accommodates a movably supported workpiece support 13 and supports a workpiece 4. To produce the workpiece 4, a beam generated by the beam emitting unit 3 melts powder 9 in a powder bed 6 above the workpiece support 4. The beam emitting unit 3 may include a beam deflector configured to deflect the generated beam onto the powder bed 6.

To allow for the melting of successive layers 7 of powder 9, a new layer 7 of powder 9 can be added to the powder bed 6 by a recoater 61 (or 62, see FIG. 2) at each melting step. Some of the powder particles in the newly applied upper layer 7 are then attached to the workpiece 4 covered by the upper layer 7 by selectively heating the powder particles using the beam emission unit 3. After the particles of the uppermost layer 7 are attached to and thereby integrated into the workpiece 4, the workpiece support 13 is lowered and the recoater 61 moves over the support opening 14 to apply a new layer 7 of powder 9.

As shown in FIG. 1, the recoater 61 may have a recoater reservoir 65. At least a portion of the powder 9 stored in the recoater reservoir 65 is added to the powder bed 6 by the recoater 61, so that the powder level in the recoater reservoir decreases each time the recoater 61 applies a new layer of powder 7 to the powder bed. The recoater reservoir 65 may be (re)filled when the powder level in the recoater reservoir 65 falls below a predetermined level and/or after each recoater step. For this purpose, the recoater reservoir 65 may be positioned below the discharge opening 22 of the intermediate reservoir 20 (referred to herein as the powder storage chamber 20 or, as mentioned above, for short, the storage chamber 20).

The dosing device 40 may be positioned between the discharge opening 22 of the storage chamber 20 and the recoater reservoir 65. The dosing device 40 can thus control the amount of powder delivered from the storage chamber 20 to the recoater reservoir 65. The dosing device 40 may be connected to a control device 100 of the powder bed fusion bonding apparatus by at least one control line 101. The control device may thus be configured to control the amount of powder delivered by the dosing device 40 to the recoater reservoir 65. In the illustrated example, the drive device 57 of the dosing device 40 is connected to the control device 100 via at least one control line 101.

Preferably, the powder bed fusion apparatus further comprises at least one main powder tank 8 connected to the powder inlet 21 of the storage chamber 20 via a powder line of the powder distribution system 6, as shown in Figures 1 and 2, or is connected to this main connection tank 8. The (second) sieve may be positioned upstream of the powder inlet 21 of the storage chamber.

The main powder tank 8 may be firmly connected to the housing surrounding the process chamber 10, the storage chamber 20, and the beam generating unit 3, or may be separate from the housing. Also, different storage chambers 20 surrounded by different housings may be collectively connected to at least one main powder tank 8. Generally, at least one main powder tank 8 may be connected to a plurality of different powder bed fusion apparatuses and configured to supply their respective storage chambers via powder supply lines.

In Figures 1 and 2, the main tank 8 is depicted as being smaller than the storage chamber 20, but in reality, it is preferable that the opposite is true, i.e., the main tank 8 is larger than the storage chamber 20.

Excess powder may be collected in an optional excess powder trap 15 on the bottom plate 11 and may be transported by the powder distribution system 6 into the storage chamber 20 via an optional sieve upstream of the powder inlet 21.

It should be noted that FIG. 1 shows two storage chambers and two metering devices. In another example, simply a single storage chamber 20 and a single metering device 40 may be employed. In this sense, the powder bed fusion apparatus may include at least one storage chamber 20. In yet another example, the storage chamber 20 may be omitted. In these examples, the metering device may receive the powder to be metered directly from the tank 8, for example, via an optional (second) sieve upstream of the metering device. For example, the powder bed fusion apparatus may include multiple storage chambers 20 and/or metering devices 40, with different storage chambers 20 and/or metering devices 40 configured to deliver different powders to the recoater (which may differ from each other in particle size and/or material composition).

FIG. 2 shows another powder bed fusion apparatus 1. This powder bed fusion apparatus 1 is very similar to the powder bed fusion apparatus 1 shown in FIG. 1, and the description of FIG. 1 can be read in conjunction with FIG. 2, except for the recoater. In FIG. 2, the recoater 62 does not have a movable reservoir like the recoater 61 shown in FIG. 1. The recoater 62 shown in FIG. 2 has a dispensing means, e.g., a blade, movably supported to move back and forth across the support opening 14, thereby dispensing a predetermined amount of powder 9 deposited on the base plate 11 of the process chamber 10, which defines the bottom of the process chamber 10. The location where the mound of powder is deposited is therefore the powder reservoir 65. This mound of powder is pushed across the support opening 14 by the recoater 62, thereby applying a new powder layer 7 to form the powder bed 6. In this sense, the location on the base plate 11 that supports the mound of powder 9 can be considered the recoater reservoir 65. As described with respect to FIG. 1, the dosing device may be positioned below the discharge opening 22 of the storage chamber 20. Thus, powder 9 in the storage chamber 20 flows onto the powder support plate 55 until a mound of powder 9 deposited on the support plate 55 blocks the discharge opening 22. Thus, the discharge opening 22 can be considered to define the powder inlet 51 of the dosing device 40.

As shown in FIG. 2, the powder support plates 55 may be connected to drivers 57 (shown as 57a and 57b). The driver 57 is preferably an ultrasonic transmitter coupled to at least one of the support plates 55, thereby coupling ultrasonic waves into the powder support plates 55. Alternatively, the driver can reciprocate the powder support plates or excite other types of vibrations in the powder support plates 55. The ultrasonic waves and/or vibrations at least partially fluidize the powder piled on the powder support plates, causing the powder to flow over the edge 551 of the powder support plates 55 facing the process chamber 10 onto the base plate 11 at location 65 (recoater reservoir 65). Therefore, edge 551 can be considered the powder outlet of the metering device 40 shown in FIG. 2.

The amount of powder 9 dispensed at position 65 can be controlled by the control device 100, for example, by the time each drive device 47 is activated, where the amplitude and frequency of the excitation are assumed to be constant, although the control device can of course also control the frequency and/or amplitude of the excitation.

Another suitable example of a metering device is shown in Figures 3 and 4. The metering device 40 can be substituted for the metering device 40 shown in Figures 1 and/or 2.

As shown in FIGS. 3 and 4, the metering device 40 may have a housing 50 with a passageway 52 defined by a passageway wall 521. The passageway wall 521 has at least a first opening 51, i.e., powder inlet 51, and a second opening 53, i.e., powder outlet 53. In other words, the passageway 52 may provide fluid communication from the powder inlet to the powder outlet (when the passageway is not filled with powder).

The passageway 52 may have a recess 522 into which the powder support frame 54 can engage, thereby maintaining the powder support in a predetermined position across the passageway 52. The powder support thus divides the passageway 52 into upper and lower sections, with the powder inlet facing upstream toward the discharge opening of the storage chamber 20 (when assembled as intended) and the powder outlet 53 facing downward toward the reservoir. In a preferred embodiment, the powder inlet is attached to the powder discharge opening 22 (see FIG. 1).

The frame 54 preferably engages the recess 522 at its periphery, and the gap between the frame 54 and the passage wall 521 is preferably sealed, for example, by at least one gasket 523. The frame 54 may support a powder support mesh 55, which may be a sieve. The mesh size of the sieve is preferably larger than the specified average particle size of the powder 9 but smaller than a critical mesh size. Therefore, unless the powder support mesh 55 is excited by the drive 47, which may be an ultrasonic transmitter and/or a vibration drive, the powder 9 falling through the storage chamber discharge opening 22 into the passage 52 accumulates on the mesh, and negligible powder falls through the mesh. However, upon activation of the drive 47, the powder falls through the mesh 55 and the lower portion of the passage 52 into (or onto) the recoater reservoir 65. As in the example shown in FIGS. 1 and 2, the drive 47 may be controlled by the control device 100 via the control line 101.

REFERENCE SIGNS LIST 1 powder bed fusion apparatus 3 beam projection unit 5 workpiece 6 powder bed 7 powder layer 8 main powder tank 9 powder 10 process chamber 11 base plate/bottom 12 process chamber housing wall 13 workpiece support 14 support opening 15 excess powder trap 16 powder transport system 20 storage chamber/intermediate reservoir 21 powder inlet of storage chamber 22 discharge opening of storage chamber 40 metering device 50 housing of metering device 51 powder inlet of metering device 52 passage of metering device 521 passage wall 522 recess in passage wall 523 gasket 53 powder outlet of metering device 54 frame 55 powder support grid/powder support plate 551 edge of powder support plate 55 56 connecting element 57a, 57b vibration drive/ultrasonic transmitter 61 Recoater (type (i))
62 Recoater (type (ii))
65 Recoater reservoir 100 Control unit 101 Control line

Claims (10)

1. A powder bed fusion apparatus comprising:
a process chamber;
a powder storage chamber having a powder drop opening connecting a volume of the powder storage chamber to the process chamber;
a recoater having a recoater reservoir within the process chamber, the recoater reservoir movably supported for movement over a support opening within the process chamber, thereby providing a new layer of powder onto a workpiece support received in the support opening;
1. A powder bed fusion apparatus comprising:
The powder bed fusion apparatus further comprises at least one metering device, the metering device comprising:
a powder inlet configured to receive powder from the powder drop opening of the powder storage chamber, the powder inlet of the metering device being positioned directly below the powder drop opening of the powder storage chamber;
a powder outlet configured to drop powder into the recoater reservoir of the powder bed fusion bonding apparatus;
a powder support disposed between the powder inlet and the powder outlet and configured to transport powder from the powder inlet to the powder outlet ;
the powder support is coupled to an ultrasonic transmitter and/or a vibration drive, the powder support comprising a mesh grid, the mesh grid being coupled to the ultrasonic transmitter and/or the vibration drive, and configured to allow powder to flow through the mesh grid by exiting the mesh grid upon operation of the ultrasonic transmitter and/or the vibration drive;
the mesh has a mesh size that is larger than the powder particles that are designated to be dispensed by the metering device, and the mesh size is smaller than a critical mesh size, which is defined as the mesh size at which the powder falls through a stationary mesh ;
the powder outlet of the metering device is positioned above the recoater reservoir when the recoater is in a parked position;
1. A powder bed fusion bonding apparatus comprising: 2. The powder bed fusion apparatus of claim 1, wherein the powder support comprises a frame, and the grid is supported by the frame. The powder bed fusion bonding apparatus of claim 2 , wherein a connecting element connects the grid network to the ultrasonic transmitter and/or the vibration driver through the frame. 4. The powder bed fusion apparatus of claim 1, wherein the metering device comprises a feeder housing having a powder passage with a passage wall, the powder passage connecting the powder inlet and the powder outlet, and the grid is positioned across the longitudinal extension of the powder passage, thereby dividing the powder passage into an upper passage portion facing the inlet and a lower passage portion facing the outlet. 5. The powder bed fusion apparatus of claim 4, wherein said passageway wall defines a recess within which said powder support sealingly engages. 6. The powder bed fusion bonding apparatus of claim 4, wherein the powder support has a recess within which the protrusion of the passage wall sealingly engages. 7. The powder bed fusion bonding apparatus of claim 4, wherein a resilient member is positioned between the powder support and the feeder housing, thereby preventing direct transmission of vibrations from the powder support to the feeder housing. 8. The powder bed fusion apparatus of claim 1, wherein the powder storage chamber has a powder inlet opening connected to a powder distribution system for conveying powder to the powder storage chamber through the powder inlet opening of the powder storage chamber, and the powder inlet opening is protected by a sieve for separating particles above a predetermined size, the sieve having a predetermined sieve mesh size. 9. The powder bed fusion apparatus of claim 8 , wherein the mesh size of the grid is larger than the sieve mesh size. 10. A method for filling a recoater reservoir of a powder bed fusion bonding apparatus according to any one of claims 1 to 9 , comprising :
(i) discharging powder from the powder reservoir onto or into a grid of the powder support;
(ii) exciting at least the grid network of the powder support of the metering device to excite ultrasonic waves in the grid network of the powder support of the metering device and/or vibrate the grid network relative to a process chamber wall, thereby transporting powder through an outlet of the metering device to the recoater reservoir;
The method, wherein the grid has a mesh size that is larger than the powder particles designated to be dispensed by the metering device, and the mesh size is smaller than a critical mesh size, which is defined as the mesh size at which the powder falls through a stationary grid.